Sołtyków, Poland – an unique palaeoecological record ot the Early Jurassic continental deposits

Abstract

The Sołtyków exposure is an old, long time abandoned clay pit. This exposure became known as a classical outcrop of alluvial-lacustrine deposits. Floral remains point to the earliest Jurassic (Lias α1-2) age, and the sequence stratigraphic correlation allows to narrow its age range to the Early Hettangian (Planorbis biochronozone). Sołtyków exposure fits the avulsion-controlled (crevassing- anastomosing) fluvial sedimentation model, however, some features such as laterally-accreted bedding point also to presence of high-sinuosity/meandering streams. Relatively thick and individualised package of lacustrine deposits occurring in the Sołtyków outcrop points to some permanency of the lake/swamp area during deposition of the sediments visible in the outcrop. Palaeosols are both of Podzol and Histosol type. The plant fossils in the Sołtyków exposure are very abundant and well preserved. The list of plants includes Neocalamites, the matoniacean, osmundacean and other indeterminate ferns, as well as pteridosperms, benettitaleans and conifers. Non-marine trace fossils comprise Coprinisphaera, Scoyeniaand aquatic Mermia ichnofacies. Other fossils that occur in Sołtyków are represented by Unionidae freshwater bivalve assemblage, insect remains, fresh-water ostracodes and scales of palaeoniscid fish. The Sołtyków exposure is well known Early Jurassic tracksite with numerous dinosaur footprints, mainly left by theropods and sauropods, and early mammalian footprints. The dinosaur nesting ground was also described. Recently, the Sołtyków exposure has been declared a natural reserve. Nature conservation problems are discussed. Due to many unique finds in Sołtyków (the oldest known evidence of gregarious ethology of dinosaurs, the biggest known Early Jurassic theropod footprints, rich and well-preserved invertebrate ichnoforms and plant remains, this exposure should be enlisted on the UNESCO World Heritage List (in geological cathegory). Moreover, the idea of “Kamienna Valley” geopark, comprising Sołtyków and other valuable outcrops in the region, is introduced.